Generally, artificial marble can be classified into two groups according to the base resin material used in the same. One group includes acrylic resin-based artificial marble, and the other group includes unsaturated polyester resin-based artificial marble. Acrylic resin based artificial marble can have desirable properties, such as excellent appearance, soft touch, excellent weather resistance, and the like, and thus there is an increased need for acrylic resin based artificial marble for various applications, including surfaces tops and other interior materials.
Generally, acrylic resin based artificial marble is prepared by mixing a mixed syrup of acrylic monomer (such methyl methacrylate and polymethyl methacrylate), inorganic filler, and marble chips (selected to provide a desired color and pattern), dissolving a polymerization initiator therein, and casting the mixture at the appropriate temperature. The acrylic monomer polymerizes to form a matrix with the marble chips dispersed therein
Different kinds of marble chips can be used to impart various colors and patterns to the artificial marble. The appearance of artificial marble provided by the marble chips can significantly affect the value of goods made using the same.
The marble chips may be obtained by pulverizing an artificial marble to form chips of various sizes. An acrylic resin, which is the same material used as a matrix for the artificial marble, may also be used as the material for the marble chips.
Recently, transparent marble chips have been used to provide an otherwise-dull artificial marble with a bright and elegant appearance, e.g. a jewel-like appearance. Accordingly, there is an increased need for transparent marble chips.
Typically transparent marble chips have been prepared from polymethylmethacrylate based resin and unsaturated polyester resin. However, such transparent marble chips may have a specific gravity of 1.15 to 1.24, which may be lower than that of the resin matrix used for the artificial marble. As a result, the transparent marble chips may float or migrate to the upper surface of the resin matrix before or during the curing process. This may result in little or no transparent marble chips at an opposite (lower) surface of the artificial stone, and the artificial marble may not exhibit uniform dispersion of the transparent marble chips. In order to compensate for this effect and distribute the transparent marble chips throughout the matrix and to the opposite surface of the artificial marble, more than twice amount of transparent marble chips should be added, which may make it difficult to control the thickness of the artificial marble.
In order to increase the specific gravity of the marble chips to the level of the matrix, inorganic fillers such as aluminum trihydrate, barium sulfate, silica, and the like may be added. However, in this case, the transparency of the marble chips can be significantly deteriorated.
Artificial marble can also be in the form of engineered stones, which are prepared from chips with a transparent appearance, e.g. mineral silica minerals such as quartz, silica, crystal, and the like, or glassy silica compounds such as glass, molten glass, and the like. Artificial marble in the form of engineered stones may have good transparency, but may also have problems resulting from the sedimentation property of the chips.
For example, the Mohs hardness of the acrylic matrix and silica and silica compounds used in engineered stones are different. Typically the artificial marble is cast in the form of a plate and the surface of the plate is sanded. Because the hardness of the matrix material and the chips is different, sanding the plate can result in an uneven surface. Accordingly, it can be difficult to use continuous manufacturing processes to make artificial marble including engineered stones as a chip material.
Accordingly, there is a need for artificial marble chips that can have a high refractive index, the same or similar specific gravity as a matrix material so that the chips can be more uniformly distributed in the matrix, can provide the artificial marble with a regular pattern without regard to the time required to cure the same, and the same or similar abrasion property as the matrix so that the artificial marble can have a good surface flatness and smoothness.